JP2008221967A - Steering hold state determination device, driver arousal level estimation device and proper course retaining device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a steering hold state determination device 10 capable of accurately determining a steering hold state of a driver. <P>SOLUTION: The steering hold state determination device consists of a torque providing means 14 for providing torque to a steering wheel 12 of a vehicle, an angle sensor 18 for detecting a steering angle of the steering wheel 12 and a steering hold state determination means 24 for determining the steering hold state of the driver based on the steering angle of the steering wheel 12 detected by the angle sensor 18 when the torque providing means 14 provides the torque. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a steering holding state determination device, a driver arousal level estimation device, and a proper course maintenance device.

In an automobile, a technique for estimating a driving state from a steering amount (steering torque, steering angle, etc.) of a steering by a driver has been proposed. For example, Patent Document 1 calculates the gripping force of the driver's hand gripping the steering unit, calculates the reaction force of the steering unit, and based on these gripping force and reaction force, slips when steering the driver's hand. A technique for predicting the occurrence of occurrence in advance is disclosed.
JP 2005-119539 A

By the way, since the driver drove in a low arousal state, there are many examples in which a recognition error or a determination error is committed and a traffic accident is caused. Therefore, development of a technique for determining the driver's arousal state is desired.
However, all of the driving state estimation techniques proposed so far including Patent Document 1 passively estimate the driving state based on information obtained from the steering behavior. With these technologies, necessary information cannot be obtained unless the driver operates the steering wheel. Therefore, it takes time to recognize the driving state of the driver on a straight road where the driver does not operate the steering wheel frequently. There is a problem.

Accordingly, an object of the present invention is to provide a steering holding state determination device that can accurately determine the steering holding state of a driver.
It is another object of the present invention to provide a driver awakening level estimation device that can accurately estimate a driver's awakening level.
It is another object of the present invention to provide an appropriate route maintenance device that can reliably maintain an appropriate route.

  In order to solve the above-described problem, the invention according to claim 1 is a torque application unit that applies torque to a vehicle steering (for example, torque application unit 14 in the embodiment) and an angle sensor that detects a steering angle of the steering. (For example, the angle sensor 18 in the embodiment) and a steering holding state for determining the steering holding state of the driver based on the steering angle of the steering detected by the angle sensor when the torque is applied by the torque applying unit. Determination means (for example, steering holding state determination means 24 in the embodiment).

  According to a second aspect of the present invention, the steering holding state determination unit is configured such that when the amount of change in the steering angle or the amount of change in the steering angle per unit time due to the torque application by the torque application unit is a predetermined value or more, the driver Is determined not to hold the steering normally.

  The invention according to claim 3 is a driver arousal level estimation device (for example, in the embodiment) including the steering holding state determination device (for example, the steering holding state determination device 10 in the embodiment) according to claim 1 or 2. A driver awakening level estimation device 20) that stores a plurality of steering angle change amounts or steering angle change amounts per unit time accompanying torque application by the torque application unit (for example, storage unit 28 in the embodiment). ), And when the change amount of the rudder angle or the change amount of the rudder angle per unit time due to the torque application by the torque application means increases with the passage of time, the driver's arousal level decreases. And a driver awakening level estimation unit (for example, a driver awakening level estimation unit 26 in the embodiment).

  The invention according to claim 4 is a driver arousal level estimation device including the steering holding state determination device according to claim 1 or 2, wherein the amount of change in the steering angle associated with torque application by the torque application unit. Alternatively, it is determined whether the amount of change in the rudder angle per unit time is equal to or greater than a threshold, and when the number of times greater than the threshold is equal to or greater than a predetermined number of times, it is determined that the driver's arousal level is decreasing. Means.

  The invention according to claim 5 includes torque applying means for applying torque to the steering of the vehicle, a torque sensor (for example, torque sensor 16 in the embodiment) for detecting the steering torque of the steering by a driver, and the torque applying means. Steering holding state determining means for determining the steering holding state of the driver based on the steering torque detected by the torque sensor when torque is applied.

  According to a sixth aspect of the present invention, there is provided a torque applying means for applying a torque to the steering, a torque sensor for detecting a steering torque of the steering by a driver, and the torque applying means so that the steering of the vehicle has a target steering angle. Steering holding state determining means for determining the steering holding state of the driver based on the steering torque detected by the torque sensor at the time of applying the torque by.

  According to a seventh aspect of the present invention, the steering holding state determining unit is configured to provide the driver when the amount of change in the steering torque accompanying the torque application by the torque application unit or the amount of change in the steering torque per unit time is equal to or less than a predetermined value. Is determined not to hold the steering normally.

  The invention according to claim 8 is a driver arousal level estimation device including the steering holding state determination device according to claim 6 or claim 7, wherein a change amount of steering torque accompanying torque application by the torque application unit or Storage means for storing a plurality of steering torque change amounts per unit time, and the change amount of the steering torque accompanying the torque application by the torque application means or the change amount of the steering torque per unit time decreases with time. And a driver arousal level estimation means for determining that the awakening level of the driver is lowered.

  The invention according to claim 9 is a driver arousal level estimation device comprising the steering holding state determination device according to claim 6 or claim 7, wherein the amount of change in steering torque accompanying torque application by the torque application means or It is determined whether the amount of change in the steering torque per unit time is equal to or less than a threshold value, and the driver arousal level is determined to be a decrease in the driver's arousal level when the threshold value is equal to or less than the predetermined number of times. And an estimation means.

  The invention according to claim 10 is characterized in that when the steering frequency of the driver is equal to or less than a predetermined value, the steering holding state is determined using the steering holding state determination device.

  The invention according to claim 11 is characterized in that the steering is rotatable independently of the tire.

  According to a twelfth aspect of the present invention, when the driver arousal level estimation means determines that the driver's arousal level is decreasing, a warning is given.

  According to a thirteenth aspect of the present invention, there is provided an appropriate course maintaining device that performs warning or steering control when the possibility that the vehicle deviates from the proper course is a predetermined value or more. When the steering holding state determining means determines that the driver does not normally hold the steering, the alarm is easily activated or the steering control is activated. It is easy to do.

  According to a fourteenth aspect of the present invention, there is provided an appropriate route maintaining apparatus that performs an alarm or steering control when the possibility that the vehicle deviates from the proper route is a predetermined value or more, and the third, fourth, eighth, ninth, tenth, 11 or 12, when the driver arousal level estimation means determines that the driver's arousal level is low, the warning level can be easily activated or the steering can be performed. It is easy to operate the control.

  The invention according to claim 15 is characterized in that the torque applying means applies a torque equivalent to the steering torque in a direction to cancel the steering torque when the steering torque by the driver is not more than a predetermined value.

  According to the first aspect of the present invention, torque is applied to the steering by the torque applying means even on a straight road or the like where the steering operation frequency is low, so that the driver operates the steering so as to cancel the applied torque. At this time, since the steering gripping force of the driver is different, a difference occurs in the steering angle. Therefore, the steering holding state of the driver can be accurately determined based on the steering angle at the time of torque application.

  In the invention according to claim 2, when the amount of change in the rudder angle accompanying the torque application or the amount of change in the rudder angle per unit time is large, the steering operation amount by the driver is small. It is possible to determine that it is not held in Therefore, the steering holding state of the driver can be accurately determined.

  In the invention according to claim 3, when the amount of change in the steering angle accompanying the torque application or the amount of change in the steering angle per unit time increases with time, the normality of the steering holding state decreases. Therefore, it can be determined that the driver's arousal level is decreasing. Therefore, the driver's arousal level can be accurately estimated.

  In the invention according to claim 4, when the change amount of the steering angle accompanying the torque application or the change amount of the steering angle per unit time is equal to or greater than the threshold value, the steering is normally maintained. It is possible to determine that the driver's arousal level has decreased because the frequency of not being increased. Therefore, the driver's arousal level can be accurately estimated.

  According to the fifth aspect of the invention, torque is applied to the steering by the torque applying means even on a straight road or the like where the steering operation frequency is low, so that the driver applies the steering torque to the steering so as to cancel the applied torque. It will be. At this time, a difference occurs in the magnitude of the steering torque that the driver exerts on the steering depending on the steering holding state of the driver. Therefore, the steering holding state of the driver can be accurately determined based on the steering torque at the time of torque application.

  According to the sixth aspect of the invention, even on a straight road with a low steering operation frequency, the torque is applied to the steering by the torque applying means so that the driver cancels the applied torque. Steering torque is applied. At this time, a difference occurs in the magnitude of the steering torque that the driver exerts on the steering depending on the steering holding state of the driver. Therefore, the steering holding state of the driver can be accurately determined based on the steering torque at the time of torque application.

  In the invention according to claim 7, when the change amount of the steering torque accompanying the torque application or the change amount of the steering torque per unit time is small, the steering torque is acting gently, so that the driver operates the steering normally. It can be determined that it is not held. Therefore, the steering holding state of the driver can be accurately determined.

  In the invention according to claim 8, when the change amount of the steering torque accompanying the torque application or the change amount of the steering torque per unit time decreases with the passage of time, the normality of the steering holding state decreases. Therefore, it can be determined that the driver's arousal level is decreasing. Therefore, the driver's arousal level can be accurately estimated.

  In the invention according to claim 9, when the change amount of the steering torque accompanying the torque application or the change amount of the steering torque per unit time is equal to or greater than a predetermined number of times, the steering is normally maintained. It is possible to determine that the driver's arousal level has decreased because the frequency of not being increased. Therefore, the driver's arousal level can be accurately estimated.

  According to the tenth aspect of the present invention, the driver arousal level estimation process can be performed only when the probability that the driver's arousal level is low is high, and the driver's discomfort can be minimized. it can.

  According to the eleventh aspect of the present invention, the running state of the vehicle can be maintained even when torque is applied to the steering by the torque applying means.

  According to the invention of claim 12, the driver's arousal level can be improved.

  According to the thirteenth aspect of the present invention, it is possible to prevent the vehicle from deviating from the proper course when the driver does not normally hold the steering.

  According to the fourteenth aspect of the present invention, it is possible to prevent the vehicle from deviating from the proper course when the driver's arousal level is low.

  According to the fifteenth aspect of the present invention, torque can be applied to the steering continuously for a long time without causing the driver to feel uncomfortable.

Hereinafter, embodiments of the present invention will be described with reference to the drawings.
(First embodiment, steering holding state determination device)
FIG. 1 is a block diagram of a steering holding state determination device, a driver arousal level estimation device, and a proper course maintenance device according to a first embodiment. In the first embodiment, the steering holding state of the driver is determined based on the steering angle with the torque application. Therefore, the steering holding state determination device 10 according to the first embodiment includes a torque applying unit 14 that applies torque to the vehicle steering 12, an angle sensor 18 that detects the steering angle of the steering 12, and torque generated by the torque applying unit 14. Steering holding state determining means 24 for determining the steering holding state of the driver based on the steering angle of the steering wheel 12 detected by the angle sensor 18 at the time of giving is provided.

  FIG. 2 is a perspective view showing the internal structure of the front portion of the vehicle. The vehicle 1 includes an angle sensor 18 that detects the steering angle of the steering 12 and a torque sensor 16 that can detect the steering torque of the steering 12. The vehicle 1 also includes a steering device 40 that drives the steered wheels 39 according to the steering angle of the steering 12. The steering device 40 is provided with an electric power steering device (hereinafter referred to as “EPS”) 37 that drives a motor and applies a steering assist force in accordance with a driver's steering input. This EPS functions as torque applying means 14 that applies torque to the steering 12.

As the steering device, a so-called steer-by-wire type steering device in which the steering wheel 12 and the steering wheel 39 are not mechanically connected may be employed. In the steer-by-wire type steering device, a road surface reaction force is not transmitted from the steered wheels 39 to the steering wheel 12, so that a motor for applying a steering reaction force (torque) to the steering wheel 12 is provided to give the driver a steering feeling. Yes. This motor or the like can be used as the torque applying means 14 in the present embodiment.
It is also possible to apply torque to the steering by controlling the wheels, suspension, etc., and giving the vehicle a behavior in the yaw direction.

  The steering 12 according to this embodiment is rotatable independently of the tire (steering wheel). That is, the tire does not interlock with the turning of the steering wheel 12 accompanying the torque application by the torque application means 14. Therefore, the running state of the vehicle can be maintained even when torque is applied to the steering by the torque applying means. This mechanism can be easily realized in a steer-by-wire steering device.

Returning to FIG. 1, the steering holding state determination apparatus according to the present embodiment includes an electronic control unit (hereinafter referred to as “ECU”) 22. The ECU 22 transmits control signals to the torque applying means 14, the torque sensor 16 and the angle sensor 18, and receives the steering torque detected by the torque sensor 16 and / or the steering angle detected by the angle sensor 18. .
The ECU 22 is provided with a steering holding state determination unit 24. The steering holding state determining means 24 determines the steering holding state of the driver based on the detected steering torque and / or steering angle in addition to the torque applied to the steering 12.

(Driver arousal estimation device)
On the other hand, the driver arousal level estimation device 20 according to the present embodiment includes a driver arousal level estimation unit 26 provided in the ECU 22 and a storage unit 28 connected to the ECU 22 in addition to the steering holding state determination device 10 described above. I have. The driver awakening level estimation means 26 determines the driver's awakening level based on the amount of change in the steering angle or the amount of change in the steering angle per unit time accompanying the torque application by the torque application means 14. The storage means 28 stores past steering angle change amount data.

  The driver awakening level estimation device 20 includes accident risk reduction means 32. The accident risk reduction unit 32 performs an operation for reducing the risk of a traffic accident based on the determination by the driver arousal level estimation unit 26. As the accident risk reduction means 32, an alarm means 34 for providing an alarm is provided.

(Proper course maintenance device)
Further, the appropriate course maintaining device according to the present embodiment includes a steering control means 36 in addition to the driver arousal level estimation device 20 described above. The steering control means 36 is also a part of the accident risk reduction means 32, and controls the steering to maintain an appropriate course based on the determination by the driver arousal level estimation means 26. As a specific control system, a lane keep assist system, an accident avoidance system, or the like can be adopted.

(Steering holding state judgment method)
Next, a steering holding state determination method, a driver arousal level estimation method, and a proper course maintenance method according to the first embodiment will be described with reference to the flowchart of FIG.
The ECU 22 monitors the operation of the steering wheel 12 by the driver via the torque sensor 16, the angle sensor 18, and the like. When the steering frequency of the driver decreases below a predetermined value, a steering holding state determination process and a driver arousal level estimation process described below are performed. Thereby, it is possible to perform the steering holding state determination process and the driver arousal level estimation process only when the probability that the steering holding state is not normal is high and the probability that the driver's awakening level is low is high, The driver's discomfort can be minimized.

  First, the ECU 22 outputs a drive signal to the torque applying means 14, and the torque applying means 14 applies torque (steering reaction force, steering reaction force, forced torque) to the vehicle steering 12 (S12).

  FIG. 4 is an explanatory diagram of various input waveforms. In the input waveform shown in FIG. 4A, torque is input in a trapezoidal shape. That is, the steering reaction force is first increased from 0 to a predetermined value with time, then the steering reaction force is maintained at a predetermined value for a predetermined time, and then the steering reaction force is decreased from the predetermined value to 0 with time. Thus, if the input amount of the steering reaction force is small and the gradient is small, the uncomfortable feeling given to the driver can be reduced. In the input waveform shown in FIG. 4B, the steering reaction force is inputted in a pulse shape. In this way, if the input amount of the steering reaction force is small and the input time is short, the uncomfortable feeling given to the driver can be reduced. In the input waveform shown in FIG. 4C, a steering reaction force proportional to the steering torque is input in the direction opposite to the direction in which the driver inputs the steering torque to the steering wheel 12. As a result, torque can be applied to the steering continuously for a long time without causing the driver to feel uncomfortable.

Note that the input waveform in FIG. 4 corresponds to not only the case of applying torque (first and second embodiments) but also the case of applying a target rudder angle (third embodiment). The reason why the vertical axis is the input target value in FIG. 4 is that the target value cannot be realized due to the steering operation of the driver (particularly when the target steering angle is given). The input waveform control method includes control amount feedforward control, applied torque feedback control, applied torque impedance control, steering angle feedback control, and the like, and any of them may be adopted.
In the following embodiments, a trapezoidal input waveform shown in FIG. 4A will be described as an example.

  FIG. 5 is a graph of input / output waveforms in the first embodiment. As the torque is applied by the torque applying means 14, the steering 12 rotates. Specifically, when torque is applied as shown in FIG. 5 (a), a steering angle is generated as shown in FIG. 5 (b). Then, ECU22 outputs a drive signal to the angle sensor 18, and the angle sensor 18 detects a steering angle (S14). The angle sensor 18 detects the steering angle every predetermined time, and based on this, the ECU 22 calculates the change amount of the steering angle accompanying the torque application and the change amount of the steering angle per unit time. The amount of change in steering angle associated with torque application (hereinafter referred to as “steering angle change width”) is an amount obtained by subtracting the steering angle before torque application from the maximum value of the steering angle during torque application. The amount of change in the rudder angle per unit time (hereinafter referred to as “steering angle change rate”) is the change speed of the rudder angle and corresponds to the gradient of the graph in FIG. The calculated steering angle change width and the steering angle change rate are stored in the storage means 28.

  When the steering steering state of the driver is not normal, the gripping force of the steering handle is reduced as compared with a normal case. Therefore, the amount by which the steering wheel 12 is rotated in accordance with the torque application, that is, the amount of change in the steering angle increases as shown by the solid line in FIG. Note that the greater the torque applied by the torque applying means, the greater the steering angle change width when the driver's steering holding state is not normal.

  Therefore, the steering holding state determination unit 24 detects the steering holding state of the driver from the input / output relationship (S16). Specifically, a threshold a for the steering angle change width is set in advance based on the magnitude of the torque applied by the torque applying means. Then, the steering angle change width calculated by the ECU 22 is compared with the threshold value a, and when the steering angle change width is equal to or greater than the threshold value a, it is determined that the driver's steering holding state is not normal.

  Further, when the driver's steering holding state is normal, the driver operates the steering 12 in a direction to cancel the rotation of the steering 12, so that the steering angle change rate is small as shown by the broken line in FIG. Become. On the other hand, when the driver's steering holding state is not normal, the steering operation is not performed in the direction in which the rotation of the steering wheel 12 is canceled. Therefore, as shown by the solid line in FIG. Will grow. Note that the greater the torque applied by the torque applying means, the greater the steering angle change rate when the driver's steering holding state is not normal.

  Therefore, the threshold value b of the steering angle change rate is set in advance based on the magnitude of the torque applied by the torque applying means. Then, the steering angle change rate calculated by the ECU 22 is compared with the threshold value b, and when the steering angle change rate is equal to or greater than the threshold value b, it is determined that the driver's steering holding state is not normal. Note that the determination of the steering holding state based on the steering angle change width (threshold value a) and the determination of the steering holding state based on the steering angle change rate (threshold value b) may be both, or only one of them may be executed. .

(Driver awareness level estimation method)
Next, the driver's arousal level is estimated (S17).
FIG. 8 and FIG. 9 are graphs showing the time change of the steering angle change width or the steering angle change rate. Hereinafter, the case of the steering angle change width will be described as an example. The arousal state and the sleep state gradually change with time. Therefore, the driver arousal level estimation means 26 reads the steering angle change width data after a predetermined time (for example, 30 minutes before the current time) out of the past steering angle change width data stored in the storage means 28. Then, as shown in FIG. 8, an approximate straight line of the read steering angle change width data is obtained by the least square method or the like. When the slope of the obtained approximate straight line becomes positive and the steering angle change width increases with time, it can be said that the normality of the driver's steering holding state tends to decrease. Therefore, in this case, it is determined that the driver is in a low arousal state (S20).

  Further, as shown in FIG. 9, a threshold for estimating the arousal level regarding the steering angle change width is set in advance. Then, the read steering angle change width data is compared with a threshold value, and if the number of steering angle change width data that is less than or equal to the threshold value is equal to or greater than a predetermined value (for example, three in FIG. 9), the driver performs steering. It can be said that there is a high frequency of not maintaining normally. Therefore, also in this case, it is determined that the driver is in a low arousal state (S20). Otherwise, it is determined that the driver is not in a low wakefulness state (S18).

  Note that the driver's arousal level can also be estimated based on the rudder angle change rate, similarly to the rudder angle change width described above. The estimation of the driver arousal level based on the rudder angle change width and the estimation of the driver awakening level based on the rudder angle change rate may be performed both or only one of them may be performed. Further, both estimation of the driver arousal level according to FIG. 8 and estimation of the driver arousal level according to FIG. 9 may be performed, or only one of them may be performed.

  If it is determined in S20 that the driver is in a low arousal state, a system for reducing the risk of an accident is activated in S22. For example, the warning is presented to the driver by the warning means 34 of the accident risk reduction means 32. As a method of presenting an alarm, a buzzer sound is emitted, an instrument panel or a room light is turned on or blinking, a front window is irradiated with light to blink, a seat belt, a seat, an accelerator pedal, etc. are vibrated. It is possible to adopt methods such as giving a steering reaction force or changing the steering angle. Thereby, the driver's arousal level can be improved.

(Proper course maintenance method)
Next, the proper course maintaining method will be described. The proper course of the host vehicle is a route on which the host vehicle should travel, as determined from surrounding conditions such as roads and obstacles, and includes the travel lane of the host vehicle. If it is difficult to maintain such a proper course, there is a risk of a traffic accident. In this case, the system that reduces the risk of accidents is made easier to operate. Specifically, the operation timing of the alarm means 34 and the steering control means 36 is made about 0.5 seconds earlier than usual. This can prevent the vehicle from deviating from the proper course when the driver does not normally hold the steering or when the driver's arousal level is reduced.

As described in detail above, the steering holding state determination device according to the present embodiment includes the torque applying means 14 that applies torque to the steering 12 of the vehicle, the angle sensor 18 that detects the steering angle of the steering 12, and the torque application. Steering holding state determination means 24 for determining the steering holding state of the driver based on the steering angle of the steering wheel 12 detected by the angle sensor 18 when the torque is applied by the means 14 is provided.
According to this configuration, torque is applied to the steering wheel 12 by the torque applying means 14 even on a straight road or the like where the operation frequency of the steering wheel 12 is low. Therefore, the relationship between the steering rudder angle change amount as an output and the torque application amount as an input. Thus, the steering holding state of the driver can be accurately determined.

Further, the steering holding state determining means is configured to determine that the driver does not normally hold the steering when the steering angle change width or the steering angle change rate is equal to or greater than a predetermined threshold.
When the steering angle change width or the steering angle change rate is large, the driver's steering gripping force is smaller than normal or it is highly likely that the driver is in a free-running operation, so the driver holds the steering normally. It is possible to determine that it is not. Therefore, the steering holding state of the driver can be accurately determined.

On the other hand, the arousal level determination means according to the present embodiment is configured to determine that the driver's arousal level is reduced when the steering angle change width or the steering angle change rate increases with time. did. Also, it is determined whether the rudder angle change width or the rudder angle change rate is equal to or greater than a threshold, and when the number is equal to or greater than a predetermined number of times, it is determined that the driver's arousal level has decreased. .
When the rudder angle change width or the rudder angle change rate increases with time, it can be determined that the normality of the steering holding state tends to decrease and the driver's arousal level has decreased. Is possible. In addition, when the steering angle change width or the steering angle change rate is equal to or greater than a predetermined number of times, the driver's arousal level is reduced because the steering is not normally held frequently. Can be determined. Therefore, the driver's arousal level can be accurately estimated.

(Second Embodiment)
Next, a steering holding state determination method and a driver arousal level estimation method according to the second embodiment will be described. In the first embodiment, the driver's steering holding state is determined based on the steering angle with the torque applied. In the second embodiment, the driver's steering holding state is determined based on the driver's steering torque with the torque applied. Is different. Note that the block diagram of FIG. 1 and the flowchart of FIG. 3 are also applicable to the second embodiment. Further, detailed description of portions having the same configuration as in the first embodiment is omitted.

  FIG. 6 is a graph showing the relationship between steering input and output in the second embodiment. When torque is applied to the steering wheel 12 by the torque applying means 14, it is possible to detect the steering torque corresponding to the handle gripping state of the driver. Specifically, a steering torque as shown in FIG. 6B is applied to the steering 12 with respect to the applied torque as shown in FIG. Therefore, the ECU 22 outputs a drive signal to the torque sensor 16, and the torque sensor 16 detects the steering torque (S14). The torque sensor 16 detects the steering torque every predetermined time, and based on this, the ECU 22 changes the steering torque change amount (hereinafter referred to as “steering torque change width”) and the steering torque change amount per unit time (hereinafter referred to as “steering torque change amount”). Hereinafter, “steering torque change rate” is calculated. The calculated steering torque change width and steering torque change rate are stored in the storage means 28.

  When the steering holding state is normal, the driver applies a steering torque that can cancel the applied torque, so that the steering torque increases as shown by a broken line in FIG. Note that as the applied torque by the torque applying means increases, the steering torque for canceling the applied torque also increases. On the other hand, when the steering holding state is not normal, the steering torque becomes small as shown by the solid line in FIG.

  Therefore, the steering holding state determination unit 24 sets a threshold a for the steering torque change width in advance based on the magnitude of the torque applied by the torque applying unit. Then, the steering torque change width calculated by the ECU 22 is compared with the threshold value a, and when the steering torque change width is equal to or less than the threshold value a, it is determined that the driver's steering holding state is not normal.

  Further, when the driver's steering holding state is normal, the driver immediately applies the steering torque, so that the steering torque change rate increases as shown by the broken line in FIG. Note that the rate of change in steering torque increases as the torque applied by the torque applying means increases. On the other hand, when the steering holding state of the driver is not normal, the steering operation is delayed, so that the steering torque change rate becomes small as shown by the solid line in FIG.

  Therefore, the threshold value b of the steering torque change rate is set in advance based on the magnitude of the torque applied by the torque applying means. Then, the steering torque change rate calculated by the ECU 22 is compared with the threshold value b, and when the steering torque change rate is equal to or higher than the threshold value b, it is determined that the driver's steering holding state is not normal. The determination of the steering holding state based on the steering torque change width (threshold value a) and the steering holding state determination based on the steering torque change rate (threshold value b) may both be performed, or only one of them may be performed. May be.

Next, the driver's arousal level is estimated (S17).
10 and 11 are graphs showing the time variation of the steering torque variation width or the steering torque variation rate. Hereinafter, the case of the steering torque change width will be described as an example. The arousal state and the sleep state gradually change with time. Therefore, the driver arousal level estimation means 26 reads the steering torque change width data after a predetermined time (for example, 30 minutes before the current time) from the past steering torque change width data stored in the storage means 28. Then, as shown in FIG. 10, an approximate straight line of the read steering torque change width data is obtained by the least square method or the like. When the slope of the obtained approximate straight line is negative and the steering torque change width is reduced, it can be said that the normality of the steering holding state of the driver tends to decrease. Therefore, in this case, it is determined that the driver is in a low arousal state (S20).

  Further, as shown in FIG. 11, a threshold for estimating arousal level related to the steering torque change width is set in advance. Then, the read steering torque change width data is compared with a threshold, and if the number of steering torque change width data that is less than or equal to the threshold is equal to or greater than a predetermined value (for example, three in FIG. 11), the driver performs steering. It can be said that there is a high frequency of not maintaining normally. Therefore, also in this case, it is determined that the driver is in a low arousal state (S20). Otherwise, it is determined that the driver is not in a low wakefulness state (S18).

  Similar to the steering torque change range described above, the driver's arousal level can also be estimated based on the steering torque change rate. The estimation of the driver arousal level based on the steering torque change width and the estimation of the driver awakening level based on the steering torque change rate may be performed both, or only one of them may be performed. Further, both estimation of the driver arousal level according to FIG. 10 and estimation of the driver arousal level according to FIG. 11 may be performed, or only one of them may be performed.

As described above in detail, the steering holding state determination device according to the second embodiment includes the torque applying means 14 that applies torque to the steering 12 of the vehicle, and the torque sensor 16 that can detect the steering torque of the steering 12 by the driver. And a steering holding state determining unit 24 that determines the steering holding state of the driver based on the steering torque detected by the torque sensor 16 when the torque is applied by the torque applying unit 14.
According to this configuration, torque is applied to the steering wheel 12 by the torque applying means 14 even on a straight road or the like where the steering 12 is operated less frequently, so that the driver applies the steering torque to the steering wheel 12 so as to cancel the applied torque. It will be. At this time, a difference occurs in the magnitude of the steering torque applied to the steering wheel 12 depending on the steering holding state of the driver. Therefore, the steering holding state of the driver can be accurately determined based on the steering torque at the time of torque application.

Further, the steering holding state determination means is configured to determine that the driver does not normally hold the steering when the steering torque change width or the steering torque change rate is equal to or less than a predetermined threshold.
When the steering torque change width or the steering torque change rate is small, it is possible to determine that the driver does not normally hold the steering because the driver gently applies the steering torque. Therefore, the steering holding state of the driver can be accurately determined.

On the other hand, the wakefulness determination means according to the present embodiment is configured to determine that the driver's wakefulness is decreased when the steering torque change width or the steering torque change rate is decreased with time. did. In addition, it is determined whether the steering torque change width or the steering torque change rate is equal to or less than a threshold value, and when the threshold value is equal to or less than the threshold value is determined a predetermined number of times, it is determined that the driver's arousal level is reduced.
When the steering torque change width or the steering torque change rate decreases with time, it can be determined that the normality of the steering holding state tends to decrease and the driver's arousal level is decreasing. Is possible. In addition, when the steering torque change width or the steering torque change rate is equal to or less than a predetermined number of times, when the number of times that the steering is not normally held is high, the driver's arousal level is reduced. It is possible to determine. Therefore, the driver's arousal level can be accurately estimated.

(Third embodiment)
Next, a steering holding state determination method and a driver arousal level estimation method according to the third embodiment will be described. In the first embodiment, the driver's steering holding state is determined based on the steering angle with the torque application, and in the second embodiment, the driver's steering holding state is determined based on the steering torque with the torque application. The third embodiment is different in that the steering holding state of the driver is determined based on the steering torque accompanying the application of torque that realizes the target steering angle. Note that the block diagram of FIG. 1 and the flowchart of FIG. 3 are also applicable to the third embodiment. Further, detailed description of portions having the same configuration as in the first or second embodiment is omitted.

The torque applying means 14 of the third embodiment applies torque to the steering so that the steering angle becomes a target value. The correspondence relationship between the target rudder angle and the applied torque is obtained in advance through experiments or the like.
When torque for realizing the target rudder angle is applied by the torque applying means 14, it is possible to detect the steering torque according to the handle gripping state of the driver. Specifically, the steering torque as shown in FIG. 7B is applied to the steering 12 with respect to the applied torque that realizes the target steering angle as shown in FIG.

  When the steering holding state is normal, the driver applies a steering torque that can cancel the applied torque, so that the steering torque increases as shown by a broken line in FIG. The steering torque increases as the target rudder angle increases. On the other hand, when the steering holding state is not normal, the steering torque becomes small as shown by the solid line in FIG.

  Therefore, the steering holding state determination unit 24 sets a steering torque change width threshold a in advance based on the target steering angle. Then, the steering torque change width calculated by the ECU 22 is compared with the threshold value a, and when the steering torque change width is equal to or less than the threshold value a, it is determined that the driver's steering holding state is not normal.

  Further, when the driver's steering holding state is normal, the driver immediately applies the steering torque, so that the steering torque change rate increases as shown by the broken line in FIG. 7B. As the target rudder angle increases, the steering torque change rate also increases. On the other hand, when the steering holding state of the driver is not normal, the driver gently applies the steering torque, so that the steering torque change rate becomes small as shown by the solid line in FIG. 7B.

  Therefore, the threshold value b of the steering torque change rate is set in advance based on the target steering angle. Then, the steering torque change rate calculated by the ECU 22 is compared with the threshold value b, and when the steering torque change rate becomes equal to or less than the threshold value b, it is determined that the steering holding state of the driver is not normal. It should be noted that both the determination of the steering holding state based on the steering torque change width (threshold value a) and the determination of the steering holding state based on the steering torque change rate (threshold value b) may be both, or only one of them may be executed. Also good.

  Note that the driver arousal level estimation method in the third embodiment can be performed based on FIG. 10 and / or FIG. 11 as in the second embodiment.

As described above in detail, the steering holding state determination device according to the third embodiment uses the torque applying means 14 for applying torque to the steering so that the steering angle becomes the target value, and the steering torque of the steering 12 by the driver. It is configured to include a detectable torque sensor 16 and a steering holding state determination unit 24 that determines the steering holding state of the driver based on the steering torque detected by the torque sensor 16 when torque is applied by the torque applying unit 14. .
According to this configuration, even on a straight road or the like where the driver operates the steering wheel 12 less frequently, the torque is applied by the torque applying means 14 so that the driver cancels the applied torque. Will act. At this time, a difference occurs in the magnitude of the steering torque applied to the steering wheel 12 depending on the steering holding state of the driver. Therefore, the steering holding state of the driver can be accurately determined based on the steering torque when the torque is applied.

The present invention is not limited to the embodiment described above.
For example, it is possible to employ other means as the steering control means other than the means for maintaining an appropriate course. For example, means for improving the straight traveling performance of the vehicle, means for improving the behavior stability of the vehicle, and the like can be employed. Further, other means other than the alarm means and the steering control means can be employed as the accident risk reduction means. For example, when the vehicle is in danger of colliding with surrounding obstacles, it is possible to make the brakes easier to operate, to maintain the vehicle at an appropriate speed, and to control the host vehicle to maintain an appropriate distance from the surrounding vehicles. It is possible to adopt a means for performing attention, a means for alerting the surroundings, a means for improving the driver's arousal level, and the like.

It is a block diagram of a steering maintenance state judging device, a driver arousal level estimating device, and a proper course maintenance device concerning a 1st embodiment. It is a perspective view which shows the internal structure of a vehicle front part. 3 is a flowchart of a steering holding state determination method, a driver arousal level estimation method, and a proper course maintenance method according to the first embodiment. It is explanatory drawing of various input waveforms. It is a graph of the input-output waveform in 1st Embodiment. It is a graph of the input-output waveform in 2nd Embodiment. It is a graph of the input-output waveform in 3rd Embodiment. It is a graph which shows the time change of the rudder angle change amount. It is a graph which shows the time change of the rudder angle change amount. It is a graph which shows the time change of steering torque change amount. It is a graph which shows the time change of steering torque change amount.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 10 ... Steering holding state determination apparatus 12 ... Steering 14 ... Torque provision means 16 ... Torque sensor 18 ... Angle sensor 20 ... Driver arousal level estimation apparatus 22 ... ECU 24 ... Steering holding state determination means 26 ... Driver arousal level estimation means 28 ... Memory Means 30 ... Proper route maintenance device 32 ... Accident risk reduction means 34 ... Alarm means 36 ... Steering control means

Claims (15)

Torque applying means for applying torque to the steering of the vehicle;
An angle sensor for detecting a steering angle of the steering;
Steering holding state determining means for determining the steering holding state of the driver based on the steering angle of the steering detected by the angle sensor when the torque is applied by the torque applying means;
A steering holding state determination device comprising: The steering holding state determining means includes
When the change amount of the steering angle or the change amount of the steering angle per unit time due to the torque application by the torque application means is a predetermined value or more, it is determined that the driver does not normally hold the steering. The steering holding state determination device according to claim 1. A driver arousal level estimation device including the steering holding state determination device according to claim 1 or 2,
Storage means for storing a plurality of steering angle change amounts or steering angle change amounts per unit time according to torque application by the torque application means;
When the amount of change in the steering angle or the amount of change in the steering angle per unit time that accompanies the torque application by the torque application means increases with the passage of time, it is determined that the driver's arousal level has decreased. Awakening level estimation means;
A driver arousal level estimation device comprising: A driver arousal level estimation device comprising the steering holding state determination device according to claim 1 or 2,
It is determined whether the amount of change in rudder angle or the amount of change in rudder angle per unit time due to the torque application by the torque application means is greater than or equal to a threshold value. Wakefulness estimation means for determining that the wakefulness is lowered;
A driver arousal level estimation device comprising: Torque applying means for applying torque to the steering of the vehicle;
A torque sensor for detecting a steering torque of the steering by a driver;
Steering holding state determining means for determining the steering holding state of the driver based on the steering torque detected by the torque sensor when torque is applied by the torque applying means;
A steering holding state determination device comprising: Torque applying means for applying torque to the steering so that the steering of the vehicle has a target steering angle;
A torque sensor for detecting a steering torque of the steering by a driver;
Steering holding state determining means for determining the steering holding state of the driver based on the steering torque detected by the torque sensor when torque is applied by the torque applying means;
A steering holding state determination device comprising: The steering holding state determining means includes
When the change amount of the steering torque accompanying the torque application by the torque application means or the change amount of the steering torque per unit time is less than or equal to a predetermined value, the driver determines that the steering is not normally held. The steering holding state determination device according to claim 6. A driver arousal level estimation device including the steering holding state determination device according to claim 6 or 7,
Storage means for storing a plurality of steering torque change amounts or steering torque change amounts per unit time associated with torque application by the torque application means;
When the amount of change in the steering torque accompanying the torque application by the torque application means or the amount of change in the steering torque per unit time decreases with time, the driver's arousal level is reduced A driver arousal level estimation means for determining;
A driver arousal level estimation device comprising: A driver arousal level estimation device including the steering holding state determination device according to claim 6 or 7,
It is determined whether the amount of change in steering torque accompanying the torque application by the torque application means or the amount of change in steering torque per unit time is less than or equal to a threshold value. A driver awakening level estimation means for determining that the driver's awakening level is reduced;
A driver arousal level estimation device comprising:   10. The driver arousal level according to claim 3, 4, 8, or 9, wherein the steering holding state is determined using the steering holding state determination device when a steering frequency of the driver is equal to or less than a predetermined value. Estimating device.   The driver awakening level estimation device according to claim 3, 4, 8, 9, or 10, wherein the steering is rotatable independently of a tire.   12. The driver wake-up according to claim 3, 4, 8, 9, 10 or 11, wherein when the driver wake-up level estimation means determines that the driver's wake-up level is lowered, an alarm is issued. Degree estimation device. When the possibility that the vehicle deviates from the proper course is a predetermined value or more, in the proper course maintenance device that performs warning or steering control,
The steering holding state determining device according to claim 1, 2, 5, 6, or 7, wherein when the driver determines that the driver does not normally hold the steering wheel, the alarm is issued. A proper course maintaining device characterized by facilitating the operation of the steering control or the steering control. When the possibility that the vehicle deviates from the proper course is a predetermined value or more, in the proper course maintenance device that performs warning or steering control,
A driver arousal level estimation device according to claim 3, 4, 8, 9, 10, 11 or 12,
When the driver arousal level estimation means determines that the driver's arousal level is decreasing, the warning is easily activated or the steering control is easily activated. apparatus. The torque applying means applies torque equivalent to the steering torque in a direction to cancel the steering torque when the steering torque by the driver is a predetermined value or less. Or the steering holding state determination device according to 7.

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